Fix #611: Add Counting Sort [C#] (#612)

* Implemented Trie C#

* Added check mark under Trie c#

* Fixed syntax

* Implemented Counting Sort [C#]

* Added counting sort to readme

* Update README.md

* Code refactoring based on PR feedback

* Fixed Travis indent size error

Author: DimaMukhin

README.md

@@ -22,7 +22,7 @@ Community (college) maintained list of Algorithms and Data Structures implementa
 | [Binary Search](https://en.wikipedia.org/wiki/Binary_search_algorithm) | [:white_check_mark:](binary_search/binary_search.c) | | [:white_check_mark:](binary_search/BinarySearch.java) | [:white_check_mark:](binary_search/binary_search.py) | [:white_check_mark:](binary_search/binary_search.go) | [:white_check_mark:](binary_search/binarySearch.js) | [:white_check_mark:](binary_search/BinarySearch.cs) |
 | [Breadth First Search](https://en.wikipedia.org/wiki/Breadth-first_search) | | | [:white_check_mark:](breadth_first_search/BreadthFirstSearch.java) | | | | |
 | [Coin Change Problem](http://www.algorithmist.com/index.php/Coin_Change) | [:white_check_mark:](coin_change_problem/coin_change_problem.c) | | [:white_check_mark:](coin_change_problem/CoinChangeProblem.java) | [:white_check_mark:](coin_change_problem/coin_change_problem.py) | [:white_check_mark:](coin_change_problem/coin_change_problem.go) | [:white_check_mark:](coin_change_problem/coinChangeProblem.js) | |
-| [Counting Sort](http://www.geeksforgeeks.org/counting-sort/)| [:white_check_mark:](counting_sort/counting_sort.c) | | [:white_check_mark:](counting_sort/CountingSort.java) | [:white_check_mark:](counting_sort/counting_sort.py) | [:white_check_mark:](counting_sort/counting_sort.go) | [:white_check_mark:](counting_sort/countingSort.js) | |
+| [Counting Sort](http://www.geeksforgeeks.org/counting-sort/)| [:white_check_mark:](counting_sort/counting_sort.c) | | [:white_check_mark:](counting_sort/CountingSort.java) | [:white_check_mark:](counting_sort/counting_sort.py) | [:white_check_mark:](counting_sort/counting_sort.go) | [:white_check_mark:](counting_sort/countingSort.js) | [:white_check_mark:](counting_sort/CountingSort.cs) |
 | [Depth First Traversal](http://www.geeksforgeeks.org/depth-first-traversal-for-a-graph/) | | | [:white_check_mark:](depth_first_traversal/DepthFirstTraversal.java) | [:white_check_mark:](depth_first_traversal/DepthFirstTraversal.py) | | | |
 | [Dijkstra Algorithm](https://en.wikipedia.org/wiki/Dijkstra's_algorithm) | [:white_check_mark:](dijkstra/dijkstra.c) | | [:white_check_mark:](dijkstra/Dijkstra.java) | [:white_check_mark:](dijkstra/dijkstra.py) | | | |
 | [Euclidean GCD](https://en.wikipedia.org/wiki/Euclidean_algorithm) | [:white_check_mark:](euclidean_gcd/euclidean_gcd.c) | | [:white_check_mark:](euclidean_gcd/EuclideanGCD.java) | [:white_check_mark:](euclidean_gcd/euclidean_gcd.py) | [:white_check_mark:](euclidean_gcd/euclidean_gcd.go) | [:white_check_mark:](euclidean_gcd/euclideanGCD.js) | [:white_check_mark:](euclidean_gcd/EuclideanGCD.cs) |
@@ -63,7 +63,6 @@ Community (college) maintained list of Algorithms and Data Structures implementa
 
 
 
-
 ## How to run them
 
 | Language | Steps |

counting_sort/CountingSort.cs

@@ -0,0 +1,43 @@
+using System;
+
+public class CountingSort
+{
+
+    /**
+    * Sorts the array using counting sort
+    * Time Complexity: O(n + k) where n is the number of elements in the array and k is the range of input
+    * Space Complexity: O(n + k)
+    */
+    public static int[] DoCountingSort(int[] arr)
+    {
+        // finding the maximum value in the array
+        int maxValue = Int32.MinValue;
+        foreach (int num in arr)
+            maxValue = Math.Max(maxValue, num);
+
+        // counting the frequency of each element in the array
+        int[] frequency = new int[maxValue + 1];
+        foreach (int num in arr)
+            frequency[num]++;
+
+        // modifying each element in the frequency array to the total of all the elements before it
+        for (int i = 1; i < frequency.Length; i++)
+            frequency[i] += frequency[i - 1];
+
+        // constructing the sorted array based on the freqency of each element in ascending order
+        int[] sortedArr = new int[arr.Length];
+        for (int i = 0; i < arr.Length; i++) {
+            sortedArr[frequency[arr[i]] - 1] = arr[i];
+            frequency[arr[i]]--;
+        }
+        return sortedArr;
+    }
+
+    public static void Main()
+    {
+        int[] arr = new int[] {10, 9, 8, 7, 6, 5, 4, 3, 2, 1};
+        int[] sortedArr = DoCountingSort(arr);
+        foreach (int num in sortedArr)
+            Console.WriteLine(num);
+    }
+}